feat: `CODEOWNERS` file #1312

Job	Run time
validation / GitHub context	2s
validation / Dependency info	7s
validation / Configuration files	7s
validation / Build coatjava	1m 47s
validation / Event generation (e_p)	1m 36s
validation / Event generation (e_gFT)	2m 39s
validation / Event generation (e_pC)	1m 53s
validation / Event generation (e_n)	1m 20s
validation / Event generation (eFT_K)	2m 12s
validation / Event generation (e_g)	2m 16s
validation / Run (e_g, rgb_fall2019)	4m 19s
validation / Run (e_p, rgb_fall2019)	4m 33s
validation / Run (eFT_K, rgb_fall2019)	5m 34s
validation / Run (e_n, rgb_fall2019)	5m 27s
validation / Run (e_gFT, rgb_fall2019)	7m 5s
validation / Run (e_pC, rgb_fall2019)	6m 13s
validation / Report multiplicity	3s
validation / Report efficiency	6s
	47m 19s

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